Submersible ultrasonic transducer assembly

ABSTRACT

An ultrasonic processing apparatus includes an ultrasonic transducer assembly comprising a submersible enclosure made of material having a low thermal conductivity. Electroacoustic transducers are coupled to an interior surface of the enclosure which is filled with a heat conductive liquid. The interior of the enclosure is traversed by tubes which establish heat transfer between the interior of the enclosure and the liquid at the outside of the enclosure and in which the assembly is immersed.

United States Patent Rissolo [54] SUBMERSIBLE ULTRASONIC [58] Field ofSearch ..3l0/8.1, 8.3, 8.7, 8.9, 9.1, 310/94; 134/1, 184; 259/] R, DIG.44, 72

References Cited UNITED STATES PATENTS Branson ..310/8.1 X Logan ..134/1Carmichael ..259/1 R Murdoch, Jr. ..259/DIG. 44

1451 Oct. 24, 1972 3,464,672 9/1969 Mas sa ..2s9/72x 2,855,526 10/1958Jones.....' ..259/DlG. 44 2,257,997 10/1941 Barnes ..259/DIG. 44 R25,l191/1962 Rawding ..259/DIG. 44 2,815,193 12/1957 Brown ..259/DIG. 44

Primary Examiner-J. D. Miller Assistant Examiner-Mark O. BuddAttorney-Ervin B. Steinberg [57] ABSTRACT An ultrasonic processingapparatus includes an ultrasonic transducer assembly comprising asubmersible enclosure made of material having a low thermalconductivity. Electroacoustic transducers are coupled to an interiorsurface of the enclosure which is filled with a heatconductive liquid.The interior of the enclosure is traversed by tubes which establish heattransfer between the interior of the enclosure and the liquid attheoutside of the enclosure and in which the assembly is immersed.

16 Claims, 4 Drawing Figures PATENTED 3.700.937

HERMAN A- RIESCVJ EM; (B.

This invention refers to ultrasonic transducer assemblies and moreparticularly to those of the submersible type used for ultrasoniccleaning and ultrasonic processing.

The use of ultrasonic energy applied to a liquid for enhancing cleaning,degreasing, plating, etching, and similar processes is well known in theart. In a typical embodiment, a stainless steel tank is fitted with oneor more ultrasonic transducer elements which are bonded to an exteriorsurface of the tank. Upon being energized with electrical energy thetransducers provide ultrasonic energy to the processing liquid confinedin the tank. This arrangement is shown, for instance, in UltrasonicEngineering (book) by Julian R. Fredrick, John Wiley & Sons, Inc., NewYork, N. Y. (l965) pages 130 to 138. The ultrasonic transducers may beeither of the magnetostrictive type or of the piezoelectric type.

When large tanks are employed, it has been found advantageous to usesubmersible transducer assemblies. In this arrangement, the transducerelements are enclosed within a liquid-tight portable enclosure, which inturn, is immersed in the treating liquid confined in the tank. Thisconstruction has the advantage that in the event a transducer assemblybecomes defective, the tank structure itself does not need to betouched, instead the defective submersible enclosure is lifted from thetank and a new assembly is put in place. The use of such submersibletransducer assemblies is well known.

For special applications it has been found necessary to use tanks madefrom material which is substantially inert to chemical attack. Intypical cases, it has been found advantageous to use tanks made frompolymeric plastic material, such as polypropylene, since such materialis largely unaffected by acids commonly used for etching processes. Themounting of a transducer assembly to the exterior wall of such a tankpresents several unique problems. Principally, the plastic material isof low thermal conductivity and the removal of heat from the bondingsurface between the transducer frontal surface and the tank wall is anecessity. Unless such heat is removed, either the bond will fail, orthe heat dissipated causes a melting of the tank wall or of the bottomat the location of transducer attachment, resulting in the destructionof the tank.

A solution for the stated problem is disclosed in US. Pat. No. 3,405,916issued to J. J. Carmichael, dated Oct. 15, 1968, entitled UltrasonicTreatment Apparatus, which patent is assigned to the present assignee.This patent reveals the use of a layer having substantially high thermalconductivity (e.g., metal) interposed in the bond between the transducerfrontal surface and the outer surface of the tank. The interposed layerextends beyond the bonding surface and conducts heat away from thebonding surface, thereby producing a solution for attaching ultrasonictransducers to a tank made of material having a relatively low thermalconductivity.

The present invention concerns a submersible transducer assembly whereinthe transducer element or elements are confined within a liquid-tightenclosure made of material having a relatively low thermal conductivity.The removal of heat from the bond between the transducer and theenclosure surface forms themajor object of this invention and, asdisclosedhereinafter, a heat exchange arrangement is shown which hasproven to be successful and reliable over many hours of service.

One of the principal objects of this invention is, therefore, theprovision of a novel submersible ultrasonic transducer assembly, theenclosure of the assembly being made of material having a substantiallylow thermal conductivity, such as polymeric plastic material.

Further and other objects of this invention will be more clearlyapparent by reference to the following description when taken inconjunction with the accompanying drawings in which:

FIG. 1 is an elevational view, partially in section, of an ultrasonicprocessing apparatus which includes submersible transducer assemblies;

FIG. 2 is a perspective view of a submersible transducer assemblyconstructed in accordance with the present invention;

FIG. 3 is an elevational sectional view through the transducer assemblyper FIG. 2, and

FIG. 4 is a detailed view showing the attachment of the ultrasonictransducer elements.

Referring now to the figures and FIG. 1 in particular, a tank 10 made,for instance, of neutral colored polypropylene or other suitable plasticmaterial, is filled with a suitable liquid 12, such as an etchant. Twosubmersible transducer assemblies 14 and 16 are suspended and immersedwithin the liquid 12 by means of a stationary beam 18, inert wires 20,and ears 22 which form a part of the submersible transducer assemblyenclosure. Each transducer assembly is connected by a respective cable24 and 24' to a suitable electrical high frequency generator 26 and 26'.As is well understood in the art, when the generator is operated,electrical high frequency energy is applied to transducer elementscontained within a respective transducer assembly and ultrasonic energy,typically in the range from l6 to 50 kHz, is transmitted to the liquid12, causing the liquid to cavitate and act upon the workpiece W which isdisposed between the transducer assemblies 14 and 16.

The construction of the submersible transducer assembly is shown moreclearly with reference to FIGS. 2, 3 and 4. The transducer assembly 16,FIG. 2, comprises essentially a rectangular housing 17, made typicallyof polypropylene plastic material. Mounted to the inside surface of onewall 17A are a plurality of ultrasonic transducers 30 which produce theultrasonic energy which is then transmitted through the wall of theenclosure 17 to the liquid 12. As shown, each transducer elementincludes piezoelectric disk means for converting the applied electricalhigh frequency energy to mechanical vibration and each of thetransducers may be constructed as has been disclosed in detail in US.Pat. No. 3,066,232, issued to Normal G. Branson dated Nov. 27, 1962,entitled Ultrasonic Transducer. It will be apparent that othertransducer assemblies may be used including those making use of themagnetostrictive effect.

The attachment of such a transducer to the surface of a plastic tank,the plastic material having relatively low thermal conductivity, isaccomplished in accordance with the disclosure in US. Pat. No.3,405,916, supra. As seen in FIG. 4, the frontal surface of eachtransducer element 30 is bonded to a metallic plate 32 by means of athin layer of epoxy resin 34 and the plate 32, in turn, is bonded to theinside surface of the plastic wall 17A by means of an epoxy layer 36.The plate 32, in a typical case, is made of aluminum in order to act asa heat sink which conducts heat away from the bonded areas.

Additionally, the assembly is provided with a plurality of verticalconduits or tubings 40 which traverse the interior of the enclosure 17and which act as heat exchange tubings as will be more clearly apparentfrom the description below. The tubings, typically, are onehalf inchpolypropylene round tubings, one-sixteenth inch wall thickness withtheir ends sealed liquid-tight to the top and bottom surfaces of theenclosure. When immersed in the liquid 12, the tubings are orientedsubstantially in a vertical direction. The inside of the submersibleassemblies 14 and 16 is filled with a suitable insulating and heatconducting medium, such as insulating oil 42, which conducts the heataway from the heat sink 32 and distributes such heat over a larger area.The tubings 40 when immersed in the treating liquid 12 provide for thenatural flow of the liquid 12 through the tubings 40 as is indicated bythe arrows 44. As the liquid 12, which is at a lower temperature, flowsthrough the tubings 40, a heat exchange takes place, that is, the heatfrom the plate 32 conducted via the heat transmitting medium (oil) tothe outside of the tubings 40 is transferred to the liquid 12 flowing atthe inside of tubings 40. The upward flow of the liquid 12 through thetubings 40 is a natural occurrence and is well understood. Thus, thetreating liquid 12 is used to cool the heat generated at the inside ofthe submersible assembly 16. In a typical example, a submersibletransducer assembly having dimensions 18 /2 by 8% by 6 inch is providedwith twelve transducer elements and with 22 heat exchange tubings. Afill pipe 46 with cap 48 is used to fill the enclosure 17 with thesuitable cooling medium, such medium being a liquid or a solid material,but suitably being an insulating, heat conducting transformer type oil.A further pipe 50 serves as a shield for the electrical cable andapplying the electrical energy to the transducer elements 30.

It will be apparent that in order to provide effective cooling throughthe heat exchange tubes, the tubings 40 must remain substantially in avertical position and that the quantity thereof must be selected toadequately cool the heat generated within the enclosure. In a typicalcase, with the dimensions described above satisfactory performance wasexperienced when for an extended period of time the liquid 12 wasmaintained in the temperature range from 150 to 200 F Additionally, itwill be understood that the submersible enclosure not only must beliquid-tight, but as indicated heretofore, the tubings 40 must be sealedliquid-tight to the end surface of the submersible enclosure.Thermoplastic material of the same kind for both the enclosure and thetubings appears to provide maximum assurance for a reliable weld orfusion joint. Standard welding techniques for thermoplastic material areused to provide such a joint. It will be apparent, moreover, thatinstead of round tubings, rectangular or square cross-sectional tubescan be used without deviating from the principle of the invention.

One of the salient features of the present invention resides in the factthat the tubings 40 have a wall thickness which is less than that of theenclosures M and 16. For the sake of rigidity and strength theenclosures must be made of relatively heavy wall thickness, typicallyone-fourth inch. Heat transfer through a plastic wall of this thicknessis difficult to achieve. By selecting relatively thin-walled tubings 40,heat is more readily transferred from the interior of the enclosure tothe exterior and since these tubings do not serve for structuralpurposes, their wall thickness can be thin.

What is claimed is:

1. An ultrasonic treatment apparatus comprising:

a. a tank;

b. a liquid disposed in said tank and adapted to act upon a workpieceimmersed in said liquid;

0. a submersible transducer assembly immersed in said liquid comprising:

c-l. a liquid-tight enclosure made of material having a relatively lowthermal conductivity;

c-2. means coupled to said enclosure for supporting said enclosure insaid liquid;

c-3. a plurality of electroacoustic transducers, each adapted to receiveelectrical energy and transmit sonic energy via a frontal surfacethereof;

0-4. means coupling each of said respective frontal surfaces in sonicenergy transmitting relation to an interior surface of said enclosure;

c-5. a heat conductive medium associated with said means coupling saidfrontal surfaces to said interior surface for conducting heat away fromthe area between a respective frontal surface and said enclosuresurface;

0-6. a plurality of tubings traversing said enclosure in a generallyvertical direction, the outer surface of said tubings being sealed inliquid-tight relation to the end surfaces of said enclosure, and theinterior of said tubings being in contact with said liquid disposed insaid tank;

c-7. a liquid heat transfer medium disposed in said enclosure andfilling the space between said tubings and said heat conductive medium;

d. electrical generator means for providing said transducers withelectrical energy, and

e. means coupling said generator means to said transducers.

2. An ultrasonic treatment apparatus as set forth in claim 1, saidtransducers operating at a frequency of at least 16 kHz.

3. An ultrasonic treatment apparatus as set forth in claim 1, said tankand said enclosure being made of polymeric plastic material.

4. An ultrasonic treatment apparatus as set forth in claim 1, saidenclosure and tubings being made of the same polymeric plastic material.

5. An ultrasonic treatment apparatus as set forth in claim 1, saidliquid disposed in said tank being an etchant.

6. An ultrasonic treatment apparatus comprising:

a. a tank adapted to contain a liquid;

b. a submersible transducer assembly adapted to be immersed in liquidcontained in said tank, said assembly comprising:

bl. a liquid-tight enclosure made of material having a relatively lowthermal conductivity;

b-2. means coupled to said enclosure for supporting said enclosure inthe tank for contact with liquid contained in said tank;

b-3. a plurality of electroacoustic transducers, each adapted to receiveelectrical energy and transmit sonic energy via a frontal surfacethereof;

b-4. means coupling each of said respective frontal surfaces in sonicenergy transmitting relation to an interior surface of said enclosure;

b-5. a heat conductive medium associated with said means coupling saidfrontal surfaces to said interior surface for conducting heat away fromthe area between a respective frontal surface and said enclosuresurface;

b-6. a plurality of tubings traversing said enclosure in a generallyvertical direction, the outer surface of said tubings being sealed inliquid-tight relation to the end surfaces of said enclosure, and theinterior of said tubings adapted to be in contact with liquid containedin said tank;

b-7. a liquid heat transfer medium disposed in said enclosure andfilling the space between said tubings and said heat conductive medium;

c. electrical generator means for providing said transducers withelectrical energy, and

d. means coupling said generator means to said transducers.

7. An ultrasonic treatment apparatus as set forth in claim 6, theresistance to heat conduction interposed by the wall thickness of saidtubings being less than that of said enclosure.

8. An ultrasonic treatment apparatus as set forth in claim 6, saidenclosure and said tubings being made of polymeric plastic material, andthe wall thickness of said tubings being less than that of saidenclosure.

9. An ultrasonic treatment apparatus as set forth in claim 8, saidenclosure and tubings being made of the same material.

10. An ultrasonic treatment apparatus which includes a transducerassembly adapted to be immersed in a liquid provided for treating aworkpiece comprismg:

a liquid-tight enclosure made of material having a relatively lowthermal conductivity;

a plurality of electroacoustic transducers, each such transducer adaptedto receive high frequency electrical energy and transmit ultrasonicenergy via a frontal surface thereof;

means coupling each of said transducers with its respective frontalsurface in sonic energy transmitting relation to an interior surface ofsaid enclosure;

a heat conducting medium filling said enclosure and being in contactwith said means coupling said transducers to said interior surface forconducting heat away from the area between a respective frontal surfaceand said enclosure surface, and

a plurality of tubings traversing said enclosure, the outer surface ofsaid tubings being in contact with said heat conducting medium fillingsaid enclosure and being sealed in liquid-tight relation to the endsurfaces of said enclosure, and the interior surface of said tubingsbeing adapted to be in contact with the 1 id in which aid enclosure 'simmersed a d 'provi i ng a conduit through which such liqu id flows whensaid transducers are operated.

11. An ultrasonic treatment apparatus as set forth in claim 10, saidenclosure being made of polymeric plastic material.

12. An ultrasonic treatment apparatus as set forth in claim 10, saidenclosure and tubings being made of the same polymeric plastic material.

13. An ultrasonic apparatus as set forth in claim 12, the wall thicknessof said tubings being less than the wall thickness of said enclosure.

14. An ultrasonic apparatus as set forth in claim 10, said heatconducting medium being an electrically insulating liquid.

15. An ultrasonic apparatus as set forth in claim 10, and means disposedon said enclosure for supporting said enclosure immersed in the liquidso that said tubings are disposed in a substantially vertical direction.

16. An ultrasonic apparatus as set forth in claim 10, said enclosure andtubings being made of material suitable for being immersed in an etchingsolution.

1. An ultrasonic treatment apparatus comprising: a. a tank; b. a liquiddisposed in said tank and adapted to act upon a workpiece immersed insaid liquid; c. a submersible transducer assembly immersed in saidliquid comprising: c-1. a liquid-tight enclosure made of material havinga relatively low thermal conductivity; c-2. means coupled to saidenclosure for supporting said enclosure in said liquid; c-3. a pluralityof electroacoustic transducers, each adapted to receive electricalenergy and transmit sonic energy via a frontal surface thereof; c-4.means coupling each of said respective frontal surfaces in sonic energytransmitting relation to an interior surface of said enclosure; c-5. aheat conductive medium associated with said means coupling said frontalsurfaces to said interior surface for conducting heat away from the areabetween a respective frontal surface and said enclosure surface; c-6. aplurality of tubings traversing said enclosure in a generally verticaldirection, the outer surface of said tubings being sealed inliquid-tight relation to the end surfaces of said enclosure, and theinterior of said tubings being in contact with said liquid disposed insaid tank; c-7. a liquid heat transfer medium disposed in said enclosureand filling the space between said tubings and said heat conductivemedium; d. electrical generator means for providing said transducerswith electrical energy, and e. means coupling said generator means tosaid transducers.
 2. An ultrasonic treatment apparatus as set forth inclaim 1, said transducers operating at a frequency of at least 16 kHz.3. An ultrasonic treatment apparatus as set forth in claim 1, said tankand said enclosure being made of polymeric plastic material.
 4. Anultrasonic treatment apparatus as set forth in claim 1, said enclosureand tubings being made of the same polymeric plastic material.
 5. Anultrasonic treatment apparatus as set forth in claim 1, said liquiddisposed in said tank being an etchant.
 6. An ultrasonic treatmentapparatus comprising: a. a tank adapted to contain a liquid; b. asubmersible transducer assembly adapted to be immersed in liquidcontained in said tank, said assembly comprising: b-1. a liquid-tightenclosure made of material having a relatively low thermal conductivity;b-2. means coupled to said enclosure for supporting said enclosure inthe tank for contact with liquid contained in said tank; b-3. aplurality of electroacoustic transducers, each adapted to receiveelectrical energy and transmit sonic energy via a frontal surfacethereof; b-4. means coupling each of said respective frontal surfaces insonic energy transmitting relation to an interior surface of saidenclosure; b-5. a heat conductive medium associated with said meanscoupling said frontal surfaces to said interior surface for conductingheat away from the area between a respective frontal surface and saidenclosure surface; b-6. a plurality of tubings traversing said enclosurein a generally vertical direction, the outer surface of said tubingsbeing sealed in liquid-tight relation to the end surfaces of saidenclosure, and the interior of said tubings adapted to be in contactwith liquid contained in said tank; b-7. a liquid heat transfer mediumdisposed in said enclosure and filling the space between said tubingsand said heat conductive medium; c. electrical generator means forproviding said transducers with electrical energy, and d. means couplingsaid generator means to said transducers.
 7. An ultrasonic treatmentapparatus as set forth in claim 6, the resistance to heat conductioninterposed by the wall thickness of said tubings being less than that ofsaid enclosure.
 8. An ultrasonic treatment apparatus as set forth inclaim 6, said enclosure and said tubings being made of polymeric plasticmaterial, and the wall thickness of said tubings being less than that ofsaid enclosure.
 9. An ultrasonic treatment apparatus as set forth inclaim 8, said enclosure and tubings being made of the same material. 10.An ultrasonic treatment apparatus which includes a transducer assemblyadapted to be immersed in a liquid provided for treating a workpiececomprising: a liquid-tight enclosure made of material having arelatively low thermal conductivity; a plurality of electroacoustictransducers, each such transducer adapted to receive high frequencyelectrical energy and transmit ultrasonic energy via a frontal surfacethereof; means coupling each of said transducers with its respectivefrontal surface in sonic energy transmitting relation to an interiorsurface of said enclosure; a heat conducting medium filling saidenclosure and being in contact with said means coupling said transducersto said interior surface for conducting heat away from the area betweena respective frontal surface and said enclosure surface, and a pluralityof tubings traversing said enclosure, the outer surface of said tubingsbeing in contact with said heat conducting medium filling said enclosureand being sealed in liquid-tight relation to the end surfaces of saidenclosure, and the interior surface of said tubings being adapted to bein contact with the liquid in which said enclosure is immersed andproviding a conduit through which such liquid flows when saidtransducers are operated.
 11. An ultrasonic treatment apparatus as setforth in claim 10, said enclosure being made of polymeric plasticmaterial.
 12. An ultrasonic treatment apparatus as set forth in claim10, said enclosure and tubings being made of the same polymeric plasticmaterial.
 13. An ultrasonic apparatus as set forth in claim 12, the wallthickness of said tubings being less than the wall thickness of saidenclosure.
 14. An ultrasonic apparatus as set forth in claim 10, saidheat conducting medium being an electrically insulating liquid.
 15. Anultrasonic apparatus as set forth in claim 10, and means disposed onsaid enclosure for supporting said enclosure immersed in the liquid sothat said tubings are disposed in a substantially vertical direction.16. An ultrasonic apparatus as set forth in claim 10, said enclosure andtubings being made of material suitable for being immersed in an etchingsolution.